KR101272333B1 - LIQUID CRYSTAL DISPLAY and DRIVING MATHOD THEREOF - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, in particular an optically compensated bend (OCB) liquid crystal display device, comprising a first substrate, a first electrode formed on the first substrate, and a second facing the first substrate. A charge formed a plurality of times by supplying charges to a first electrode, a second electrode formed on the second substrate and facing the first electrode, a liquid crystal layer injected between the first and second electrodes, and the first electrode. It includes a plurality of charge supply for applying a bend voltage for transferring the liquid crystal orientation of the liquid crystal layer. Accordingly, in the OCB liquid crystal display, the liquid crystal layer may be transferred to the bending orientation in a short time by repeatedly supplying a charge corresponding to the bend voltage to the liquid crystal capacitor and uniformly applying the bend voltage to the entire common electrode.

Bent, OCB, Liquid Crystal Display, Charge Supply

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY and DRIVING MATHOD THEREOF}

1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention.

2 is an equivalent circuit diagram of a pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a layout view of a liquid crystal panel assembly according to an exemplary embodiment of the present invention.

4 is a cross-sectional view of the liquid crystal panel assembly of FIG. 3 taken along line IV-IV.

5 is a diagram illustrating an alignment state of the liquid crystal before applying the bend voltage.

6 is a diagram illustrating an alignment state of the liquid crystal after applying the bend voltage.

7 is a circuit diagram illustrating a charge supply unit according to an exemplary embodiment of the present invention.

8 is a signal waveform diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, in particular an OCB (optically compensated bend) type liquid crystal display.

2. Description of the Related Art [0002] A liquid crystal display device is one of the most widely used flat panel display devices, and includes two display panels having field generating electrodes such as a pixel electrode and a common electrode, and a liquid crystal layer interposed therebetween. The liquid crystal display displays an image by applying a voltage to the electric field generating electrode to generate an electric field in the liquid crystal layer, thereby determining the direction of the liquid crystal molecules in the liquid crystal layer and controlling the polarization of the incident light.

Various methods have been proposed to improve the response speed and the reference viewing angle among the liquid crystal displays, and examples thereof include an OCB (optically compensated bend) type liquid crystal display.

In the OCB type liquid crystal display, when the electric field is applied to the two field generating electrodes, the liquid crystal molecules are symmetrical with respect to the center plane between the two substrates and change from a horizontal array to a vertical array from the substrate plane to the center plane so that a wide reference viewing angle is obtained. Can be obtained.

However, the OCB type liquid crystal display is not stable unlike other liquid crystal modes, and has a splay orientation in a state in which no voltage is applied, and it has to be transferred to the bent orientation.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an OCB liquid crystal display device capable of transitioning from a splay orientation to a bent orientation for a short time when power is supplied.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes a first substrate, a first electrode formed on the first substrate, a second substrate facing the first substrate, and a second substrate on the second substrate. The liquid crystal layer of the liquid crystal layer is formed by supplying charge to the second electrode facing the first electrode, the liquid crystal layer injected between the first and second electrodes, and the first electrode a plurality of times. It includes a plurality of charge supply for applying a bend voltage to make.

By the alignment transition of the liquid crystal, the alignment of the liquid crystal may be converted from splay alignment to bend alignment.

The charge supply unit may apply the bend voltage to the first electrode before the display panel displays an image.

The charge supply unit may apply a common voltage to the first electrode while the display panel displays an image.

The charge supply unit includes a capacitor connected between the common voltage source and the reference node, a first switching element connected between the bend voltage source and the reference node, and a second switching element connected between the reference node and the first electrode. It may include.

The first and second switching elements may be alternately turned on.

The bend voltage may be higher than the common voltage.

The charge supply unit may further include a third switching device connected between the common voltage and the first electrode, and the third switching device may be turned on after the first electrode is charged to the bend voltage.

The bend voltage may increase in voltage level with time.

In addition, a method of driving a liquid crystal display according to an exemplary embodiment of the present invention may include a first substrate, a first electrode formed on the first substrate, a second substrate facing the first substrate, and a second substrate on the second substrate. In the driving method of the liquid crystal display device including a liquid crystal layer which is formed and is injected between the first electrode and the first electrode, and the first and second electrodes, the first electrode is charged a plurality of times Applying a bend voltage for transitioning the liquid crystal alignment of the liquid crystal layer by supplying a voltage, applying a common voltage to the first electrode, and applying a data voltage to the second electrode to display an image. .

The liquid crystal display includes a capacitor connected between a common voltage source and a reference node, a first switching element connected between a bend voltage source and the reference node, and a second switching connected between the reference node and the first electrode. And a charge supplying step, wherein the first switching device is turned on to supply the bend voltage to a capacitor to charge an electric charge, and the second switching device is turned on to charge the first charged charge. And supplying to the electrode.

The bend voltage may have a voltage level higher than the common voltage.

The bend voltage may increase in voltage level with time.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: FIG. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

First, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel in the liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a data driver 500 connected thereto. The gray voltage generator 800, the charge supply 700, and the signal controller 600 controlling the gray voltage generator 800 connected thereto are included.

The liquid crystal panel assembly 300 includes a plurality of signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels PX connected to the plurality of signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. Include. 2, the liquid crystal display panel assembly 300 includes lower and upper display panels 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

The signal lines G ₁ -G _n and D ₁ -D _m include a plurality of gate lines G ₁ -G _n for transferring gate signals (also referred to as "scan signals") and a plurality of data lines D ₁ -D _m ). The gate lines G _{1 to} G _n extend in a substantially row direction and are substantially parallel to each other, and the data lines D _{1 to} D _m extend in a substantially column direction and are substantially parallel to each other.

Each pixel PX, for example, is connected to the i-th (i = 1, 2, ..., n) gate line G _i and the j-th (j = 1, 2, ..., m) data line D _j . The pixel PX includes a switching element Q connected to the signal lines G _i and D _j , a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. The storage capacitor Cst can be omitted if necessary.

The switching element Q is a three terminal element such as a thin film transistor provided in the lower panel 100. The control terminal is connected to the gate line G _i and the input terminal is connected to the data line D _j And the output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst. The thin film transistor may include polycrystalline silicon or amorphous silicon.

The liquid crystal capacitor Clc has two terminals, the pixel electrode 191 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 191 and 270 is a dielectric material. Function as. The pixel electrode 191 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives the common voltage Vcom. 2, the common electrode 270 may be provided on the lower panel 100. At this time, at least one of the two electrodes 191 and 270 may be linear or bar-shaped.

The storage capacitor Cst serving as an auxiliary capacitor of the liquid crystal capacitor Clc is formed by superimposing a separate signal line (not shown) and a pixel electrode 191 provided on the lower panel 100 with an insulator interposed therebetween, A predetermined voltage such as the common voltage Vcom is applied to the separate signal lines. However, the storage capacitor Cst may be formed by overlapping the pixel electrode 191 with the previous gate line immediately above via an insulator.

On the other hand, in order to implement color display, each pixel PX uniquely displays one of primary colors (space division), or each pixel PX alternately displays a basic color (time division) So that the desired color is recognized by the spatial and temporal sum of these basic colors. Examples of basic colors include red, green, and blue. 2 shows that each pixel PX has a color filter 230 indicating one of the basic colors in an area of the upper panel 200 corresponding to the pixel electrode 191 as an example of space division. 2, the color filter 230 may be disposed above or below the pixel electrode 191 of the lower panel 100. [

At least one polarizer (not shown) for polarizing light is attached to an outer surface of the liquid crystal panel assembly 300.

Next, the detailed structure of the liquid crystal panel assembly 300 will be described in detail with reference to FIGS. 3 and 4.

3 is a layout view of a liquid crystal panel assembly according to an exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view of the liquid crystal panel assembly of FIG. 3 taken along line IV-IV.

As shown in FIG. 3, the liquid crystal panel assembly according to the exemplary embodiment includes a lower panel 100, an upper panel 200, and a liquid crystal layer 3 interposed therebetween.

First, the lower panel 100 will be described.

A plurality of gate lines 121 and a plurality of storage electrode lines 131 are formed on an insulating substrate 110 made of transparent glass or plastic.

The gate line 121 transmits the gate signal and extends mainly in the horizontal direction. Each gate line 121 includes a plurality of gate electrodes 124 protruding downward and end portions (not shown) having a large area for connection with another layer or an external driving circuit. A gate driving circuit (not shown) for generating a gate signal may be mounted on a flexible printed circuit film (not shown) attached on the substrate 110, directly mounted on the substrate 110, And may be integrated on the substrate 110. When the gate driving circuit is integrated on the substrate 110, the gate line 121 may extend and be directly connected thereto.

The storage electrode line 131 receives a predetermined voltage, and includes a stem line extending substantially in parallel with the gate line 121 and a plurality of pairs of storage electrodes 133a and 133b separated therefrom. Each of the storage electrode lines 131 is positioned between two adjacent gate lines 121, and the stem line is closer to the lower side of the two gate lines 12. Each of the sustain electrodes 133a and 133b has a fixed end connected to a stem line and a free end opposite to the fixed end. However, the shape and arrangement of the sustain electrode lines 131 can be variously modified.

The gate line 121 and the storage electrode line 131 may be formed of a metal such as aluminum (Al) or an aluminum alloy, a metal such as silver (Ag) or silver alloy, a copper metal such as copper or copper alloy, Such as molybdenum metal, chromium (Cr), tantalum (Ta), and titanium (Ti), such as molybdenum (Mo) or molybdenum alloy. However, they may have a multi-film structure including two conductive films (not shown) having different physical properties. One of the conductive films is made of a metal having a low resistivity, for example, an aluminum-based metal, a silver-based metal, or a copper-based metal to reduce signal delay and voltage drop. Alternatively, the other conductive film is made of a material having excellent physical, chemical and electrical contact properties with other materials, particularly indium tin oxide (ITO) and indium zinc oxide (IZO), such as molybdenum metal, chromium, tantalum and titanium. A good example of such a combination is a chromium bottom film, an aluminum (alloy) top film, an aluminum (alloy) bottom film and a molybdenum (alloy) top film. However, the gate line 121 and the sustain electrode line 131 may be made of various other metals or conductors.

Side surfaces of the gate line 121 and the storage electrode line 131 are inclined with respect to the surface of the substrate 110, and the inclination angle is preferably about 30 ° to about 80 °.

A gate insulating layer 140 made of silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the gate line 121 and the storage electrode line 131.

A plurality of island-shaped semiconductors 154 made of hydrogenated amorphous silicon (abbreviated as a-Si for amorphous silicon) or polycrystalline silicon (polysilicon) are formed on the gate insulating film 140. The semiconductor 154 is positioned over the gate electrode 124.

A plurality of island type ohmic contacts 163 and 165 are formed on the semiconductor 154. The resistive contact members 163 and 165 may be made of a material such as n + hydrogenated amorphous silicon, or may be made of silicide, which is heavily doped with phosphorous n-type impurities. The resistive contact members 163 and 165 are arranged on the semiconductor 154 in pairs.

Side surfaces of the semiconductor 154 and the ohmic contacts 163 and 165 are also inclined with respect to the surface of the substrate 110, and the inclination angle is about 30 ° to 80 °.

A plurality of data lines 171 and a plurality of drain electrodes 175 are formed on the ohmic contacts 163 and 165 and the gate insulating layer 140.

The data line 171 transmits a data signal and mainly extends in the vertical direction to cross the gate line 121. Each data line 171 also crosses the storage electrode line 131 and runs between adjacent sets of storage electrodes 133a and 133b. Each data line 171 also intersects the stem line of the storage electrode line 131. Each data line 171 includes a wide end portion (not shown) for connecting a plurality of source electrodes 173 extending toward the gate electrode 124 with another layer or an external driving circuit. do. A data driving circuit (not shown) for generating a data signal is mounted on a flexible printed circuit film (not shown) attached to the substrate 110, directly mounted on the substrate 110, or integrated in the substrate 110. Can be. When the data driving circuit is integrated on the substrate 110, the data line 171 can extend and be directly connected thereto.

The drain electrode 175 is separated from the data line 171 and faces the source electrode 173 with the gate electrode 124 as a center.

One gate electrode 124, one source electrode 173 and one drain electrode 175 constitute one thin film transistor (TFT) Q together with the semiconductor 154, and the thin film transistor Q are formed in the semiconductor 154 between the source electrode 173 and the drain electrode 175. [

The data line 171 and the drain electrode 175 are preferably made of a refractory metal such as molybdenum, chromium, tantalum, and titanium or an alloy thereof. The refractory metal film (not shown) (Not shown). ≪ / RTI > Examples of the multilayer structure include a double layer of chromium or molybdenum (alloy) lower layer and an aluminum (alloy) upper layer, a triple layer of molybdenum (alloy) lower layer and an aluminum (alloy) interlayer and molybdenum (alloy) upper layer. However, the data line 171 and the drain electrode 175 may be made of various other metals or conductors.

It is preferable that the data line 171 and the drain electrode 175 are also inclined at an inclination angle of about 30 DEG to 80 DEG with respect to the substrate 110 surface.

The resistive contact members 163 and 165 exist only between the semiconductor 154 under the resistive contact members 163 and 165 and the data line 171 and the drain electrode 175 thereon and lower the contact resistance therebetween.

A passivation layer 180 is formed on the data line 171, the drain electrode 175, and the exposed semiconductor 154. The protective film 180 is made of an inorganic insulating material or an organic insulating material and may have a flat surface. Examples of the inorganic insulating material include silicon nitride and silicon oxide. The organic insulating material may have photosensitivity and its dielectric constant is preferably about 4.0 or less. However, the passivation layer 180 may have a double layer structure of the lower inorganic layer and the upper organic layer so as not to damage the exposed portion of the semiconductor 154 while maintaining excellent insulating properties of the organic layer.

The passivation layer 180 is formed with a plurality of contact holes (not shown) respectively exposing an end portion (not shown) of the data line 171. The passivation layer 180 and the gate insulating layer 140 are formed in the passivation layer 180. A plurality of contact holes (not shown) are formed to expose end portions (not shown) of the gate line 121.

A plurality of pixel electrodes 191 and a plurality of contact assistants (not shown) are formed on the passivation layer 180. They may be made of a transparent conductive material such as ITO or IZO or a reflective metal such as aluminum, silver, chromium or an alloy thereof.

The pixel electrode 191 is physically and electrically connected to the drain electrode 175 through the contact hole 185 and receives a data signal from the drain electrode 175. The pixel electrode 191 to which the data signal is applied generates an electric field together with the common electrode 270 of the other display panel 200 to which the common voltage is applied, thereby generating an electric field between the two electrodes 191 and 270. The direction of the liquid crystal molecules 31 of the liquid crystal layer 3 is determined. The polarization of light passing through the liquid crystal layer 3 varies according to the direction of the liquid crystal molecules 31 determined as described above. The pixel electrode 191 and the common electrode 270 form a liquid crystal capacitor to maintain an applied voltage even after the thin film transistor is turned off.

The pixel electrode 191 overlaps the storage electrode line 131 including the storage electrodes 133a and 133b, and the left and right sides of the pixel electrode 191 are adjacent to the data line 171 than the storage electrodes 133a and 133b. do. The pixel electrode 191 and the drain electrode 175 electrically connected to the pixel electrode 191 overlap with the storage electrode line 131 to form a storage capacitor that enhances the voltage holding capability of the liquid crystal capacitor.

The contact auxiliary member (not shown) is connected to an end portion (not shown) of the gate line 121 and an end portion (not shown) of the data line 171 through contact holes (not shown), respectively. The contact auxiliary member (not shown) compensates for and protects an end portion (not shown) of the gate line 121 and an end portion (not shown) of the data line 171 and an external device.

Next, the upper panel 200 will be described.

A black matrix 220 is formed on an insulating substrate 210 made of transparent glass, plastic, or the like. The black matrix 220 includes a linear portion (not shown) corresponding to the data line 171 and a planar portion (not shown) corresponding to the thin film transistor, and prevents light leakage between the pixel electrodes 191.

A plurality of color filters 230 are further formed on the substrate 210. The color filter 230 is mostly present in an area surrounded by the black matrix 220, and may extend in the vertical direction along the column of the pixel electrodes 191. Each color filter 230 may display one of primary colors such as three primary colors of red, green, and blue.

An overcoat may be formed on the color filter 230 and the black matrix 220. The overcoat may be made of an organic insulator, which prevents the color filter 230 from being exposed and provides a flat surface.

The common electrode 270 is formed on the color filter 230 and the black matrix 220. The common electrode 270 is made of a transparent conductor such as ITO or IZO.

Inner surfaces of the display panels 100 and 200 are coated with horizontal alignment layers 11 and 21 which are rubbed in the same direction.

Polarizers 12 and 22 are provided on the outer surfaces of the display panels 100 and 200, and the transmission axes of the two polarizers 12 and 22 are orthogonal and one of the transmission axes is parallel to the gate line 121. desirable. In the case of the reflection type liquid crystal display device, one of the two polarizers 12 and 22 may be omitted.

A compensation film may be attached between the polarizers 12 and 22 and the display panels 100 and 200, and a C plate compensation film or a biaxial compensation film may be used as the compensation film.

The liquid crystal layer 3 includes a nematic liquid crystal having a positive dielectric anisotropy, and is initially oriented in a splay orientation and then converted to a bend orientation as shown in FIG. 4 by a bend voltage, and driving for display is performed in this state. In general, the OCB liquid crystal display displays normally white, that is, white without applying a voltage.

Referring again to FIG. 1, the gradation voltage generator 800 generates the total gradation voltage related to the transmittance of the pixel PX or a limited number of gradation voltages (hereinafter referred to as "reference gradation voltage"). The reference gray level voltage may include a positive value and a negative value with respect to the common voltage Vcom.

The gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 and supplies a gate signal composed of a combination of the gate-on voltage Von and the gate-off voltage Voff to the gate line G ₁ -G _n .

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300 and selects the gradation voltage from the gradation voltage generator 800 and supplies the selected data voltages to the data lines D ₁ -D _m . However, when the gray voltage generator 800 does not provide all of the gray voltages but provides only a limited number of reference gray voltages, the data driver 500 divides the reference gray voltages to generate a desired data voltage.

The charge supply unit 700 includes a plurality of charge supply circuits 710 positioned in an edge region of the lower panel 100. The charge supply unit 700 applies a common voltage or a bend voltage to the common electrode 270 of the upper panel 200 through a short point (not shown) of the lower panel 100.

Each charge supply circuit 710 will be described in detail later.

The signal controller 600 controls the gate driver 400, the data driver 500, the charge supply unit 700, and the like.

Each of the driving devices 400, 500, 600, 700, and 800 may be mounted directly on the liquid crystal panel assembly 300 in the form of at least one integrated circuit chip, or may be a flexible printed circuit film (not shown). It may be mounted on the liquid crystal panel assembly 300 in the form of a tape carrier package (TCP), or mounted on a separate printed circuit board (not shown). Alternatively, these driving devices 400, 500, 600, 700, and 800 are connected to the liquid crystal panel assembly 300 together with the signal lines G ₁ -G _n , D ₁ -D _m and the thin film transistor switching element Q. It may be integrated. In addition, the drivers 400, 500, 600, 700, 800 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside of a single chip.

Hereinafter, the alignment transition of the liquid crystal layer 3 using the charge supply unit 700 will be described with reference to FIGS. 5 to 8.

5 is a diagram illustrating an alignment state of the liquid crystal before applying the bend voltage, and FIG. 6 is a diagram illustrating an alignment state of the liquid crystal after applying the bend voltage.

Referring to FIG. 5, in a state in which no bend voltage is applied, the liquid crystal molecules 31 near the two alignment layers 11 and 21 have a pretilt angle ?? of one end in a direction toward the rubbing direction. Is oriented. Therefore, the arrangement of the liquid crystal molecules 31 is symmetrical about the plane parallel to the planes of the substrates 110 and 210 and at approximately the same distance from the surfaces of the two alignment layers 11 and 21 (hereinafter referred to as the "center plane"). do. This orientation is called splay orientation.

In this state, when an electric field is applied to the liquid crystal layer 3, the liquid crystal molecules 31 are changed from the splay orientation to another orientation.

When voltage is applied to the electrodes (not shown) of the two display panels 100 and 200, and an electric field perpendicular to the surfaces of the two display panels 100 and 200 is generated in the liquid crystal layer 3, the alignment layers 11 and 21 are near. Liquid crystal molecules 31 rise in response to the electric field. However, since the directions in which the surfaces of the two alignment layers 11 and 21 rise are the same, the directions in which the liquid crystal molecules 31 rise in the middle portion of the liquid crystal layer 3 collide with each other to generate a large stress, thereby resulting in an energy stable twist ( transition to twist orientation. This is called a transition splay orientation.

In this state, if the electric field is made stronger, the liquid crystal is in a bent orientation as shown in FIG. 6. Such an alignment transition should occur uniformly in the liquid crystal capacitor Clc of the entire liquid crystal panel assembly 300.

FIG. 7 is a circuit diagram illustrating a charge supply circuit according to an exemplary embodiment of the present invention, and FIG. 8 is a signal waveform diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 7, each charge supply circuit 710 includes a capacitor C and a plurality of switching elements S1, S2, and S3.

The switching device S1 is a three-terminal device, and includes a control terminal connected to the first control signal G1, an input terminal connected to the common voltage Vcom, and an output terminal connected to the output terminal OUT. .

The switching element S2 is also a three-terminal element, and includes a control terminal connected with the second control signal G2, an input terminal connected with the bend voltage Vbend, and an output terminal connected with the node n1. do.

The switching element S3 is also a three-terminal element, and includes a control terminal connected with the third control signal G3, an input terminal connected with the node n1, and an output terminal connected with the output terminal OUT. .

The capacitor C is connected between the common voltage Vcom and the node n1.

Output terminals OUT of the plurality of charge supply circuits 710 are connected to the common electrode 270 of the upper panel 200 through a short point of the lower panel 100.

Next, an operation of such a liquid crystal display will be described in detail with reference to FIG. 7.

When a power input signal (not shown) is recognized from the outside, the signal controller 600 outputs the orientation control signal CONT3 to the charge supply unit 700.

The alignment control signal CONT3 includes first to third control signals G1, G2, and G3.

First, when the high level second control signal G2 is applied, the switching element S2 of each charge supply circuit 710 is turned on to transfer the bend voltage Vbend to the node n1. The bend voltage Vbend is a DC voltage and has a higher level than the common voltage Vcom.

Capacitor C charges a charge corresponding to the difference voltage between common voltage Vcom and bend voltage Vbend.

Next, when the third control signal G3 having the high level is applied and the second control signal G2 transitions to the low level, the switching element S2 is turned off and the switching element S3 is turned on.

As a result, current flows between the capacitor C and the liquid crystal capacitor Clc, and charges charged in the capacitor C are transferred to the common electrode 270 through the output terminal OUT to charge the liquid crystal capacitor Clc.

When the operation of the switching elements S2 and S3 is repeated a plurality of times, a large amount of charge is charged in the liquid crystal capacitor Clc, so that the common electrode 270 is uniformly supplied with a voltage having the same level as the bend voltage Vbend. Have Therefore, the liquid crystal layer 3 transitions to the bending orientation according to the electric field corresponding to the bend voltage Vbend.

At this time, as the voltage Vcom _real of the common electrode 270 approaches the bend voltage Vbend, the current peaks of both capacitors C and Clc are gradually lowered, and accordingly, the liquid crystal capacitor in the capacitor C is reduced. The amount of charge transferred to (Clc) is reduced. Therefore, as the on / off of the switching elements S2 and S3 is repeated, the level of the bend voltage Vbend may be increased to increase the amount of mobile charge between the capacitors C and Clc, and the liquid crystal capacitor Clc may be It can be filled uniformly.

On the other hand, while the switching elements S2 and S3 repeat the turn on / off, the switching element S1 maintains the turn off state.

When the liquid crystal layer 3 finishes the alignment transition, the first and second control signals G1 and G2 transition to a low level, and the third control signal G3 transitions to a high level.

Accordingly, the switching elements S2 and S3 are turned off, the switching element S1 is turned on, and the common voltage Vcom is applied to the common electrode 270 through the output terminal OUT.

In a state in which the common voltage Vcom is applied to the common electrode 270, the signal controller 600 controls an input image signal R, G, B and its display from an external graphic controller (not shown). Receive the control signal. The input image signals R, G and B contain luminance information of each pixel PX and the luminance has a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ) 2 ⁶ ) gray levels. Examples of the input control signal include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 600 properly processes the input image signals R, G, and B according to operating conditions of the liquid crystal panel assembly 300 based on the input image signals R, G, and B and the input control signal, and controls the gate. After generating the signal CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal CONT2 and the processed image signal DAT are transmitted to the data driver 500. Export to).

The gate control signal CONT1 includes at least one clock signal for controlling the output period of the scan start signal STV indicating the start of scanning and the gate-on voltage Von. The gate control signal CONT1 may further include an output enable signal OE that defines the duration of the gate on voltage Von.

The data control signal CONT2 includes a horizontal synchronization start signal STH for notifying the start of the transmission of the digital video signal DAT to the pixel PX of one row and an analog data voltage for the data lines D _{1 to} D _m The load signal LOAD and the data clock signal HCLK. The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the analog data voltage relative to the common voltage Vcom (hereinafter referred to as " polarity of the data voltage " RVS) may be further included.

The data driver 500 receives the digital video signal DAT for one row of the pixels PX in accordance with the data control signal CONT2 from the signal controller 600 and outputs the digital video signal DAT corresponding to each digital video signal DAT And converts the digital video signal DAT into an analog data voltage and applies it to the corresponding data lines D ₁ -D _m .

The gate driver 400 applies the gate-on voltage Von to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n . Turn on the switching element (Q) connected to. Then, the data voltage applied to the data lines D ₁ -D _m is applied to the pixel PX through the turned-on switching element Q.

The difference between the data voltage applied to the pixel PX and the common voltage Vcom appears as the charging voltage of the liquid crystal capacitor Clc, that is, the pixel voltage. The liquid crystal molecules have different arrangements according to the magnitude of the pixel voltage, and thus the polarization of light passing through the liquid crystal layer 3 changes. The change in polarization is represented by a change in the transmittance of light by a polarizer attached to the display panel assembly 300, whereby the pixel PX displays the luminance represented by the gray level of the image signal DAT.

This process is repeated in units of one horizontal period (also referred to as "1H" and equal to one period of the horizontal sync signal Hsync and the data enable signal DE), thereby all the gate lines G ₁ -G _n. ), The gate-on voltage Von is sequentially applied, and the data voltage is applied to all the pixels PX to display an image of one frame.

When one frame ends, the next frame starts and the state of the inversion signal RVS applied to the data driver 500 is controlled such that the polarity of the data voltage applied to each pixel PX is opposite to the polarity of the previous frame "Frame inversion"). In this case, the polarities of the data voltages flowing through one data line may be changed (eg, row inversion and point inversion), or polarities of data voltages applied to one pixel row may be different depending on the characteristics of the inversion signal RVS within one frame. (Eg: column inversion, point inversion).

As described above, in the OCB liquid crystal display, the liquid crystal layer may be transferred to the bent alignment in a short time by repeatedly supplying a charge corresponding to the bend voltage to the liquid crystal capacitor and uniformly applying the bend voltage to the entire common electrode.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (13)

The first substrate, A first electrode formed on the first substrate, A second substrate facing the first substrate, A second electrode formed on the second substrate and facing the first electrode, A liquid crystal layer injected between the first and second electrodes, A plurality of charge supply unit for applying a bend voltage for changing the liquid crystal orientation of the liquid crystal layer by supplying charge to the first electrode a plurality of times Including, The charge supply unit A capacitor connected between the common voltage source and the reference node, A first switching element connected between the bend voltage source and the reference node, and A second switching element connected between the reference node and the first electrode Liquid crystal display comprising a. In claim 1, Liquid crystal display device wherein the alignment of the liquid crystal is converted from the splay alignment to the bend alignment by the alignment transition of the liquid crystal. 3. The method of claim 2, And the charge supply unit applies the bend voltage to the first electrode before the liquid crystal display displays an image. 4. The method of claim 3, And the charge supply unit applies a common voltage to the first electrode while the liquid crystal display displays an image. delete In claim 1, The first and second switching elements are alternately turned on. In claim 6, The bend voltage is a voltage higher than the common voltage. 8. The method of claim 7, The charge supply unit further includes a third switching element connected between the common voltage and the first electrode, And the third switching element is turned on after the first electrode is charged with the bend voltage. In claim 8, The bend voltage is a liquid crystal display device that the voltage level increases with time. A first substrate, a first electrode formed on the first substrate, a second substrate facing the first substrate, a second electrode formed on the second substrate and facing the first electrode, and the first substrate In the driving method of the liquid crystal display device including the liquid crystal layer injected between the 1st and 2nd electrode, Applying a bend voltage to transfer the liquid crystal alignment of the liquid crystal layer by supplying charge to the first electrode a plurality of times; Applying a common voltage to the first electrode, and Displaying an image by applying a data voltage to the second electrode Including, The liquid crystal display includes a capacitor connected between a common voltage source and a reference node; A first switching element connected between the bend voltage source and the reference node, and A second switching element connected between the reference node and the first electrode, The charge supply step The first switching element is turned on to supply the bend voltage to a capacitor to charge an electric charge, and Supplying charged charge to the first electrode by turning on the second switching device Method of driving a liquid crystal display comprising a. delete In claim 10, And the bend voltage has a voltage level higher than the common voltage. The method of claim 12, The bend voltage is a driving method of the liquid crystal display device in which the voltage level increases with time.

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